You don't have to accept the Summoner's Code to play, but that doesn't matter. You DO have to accept the EULA, which includes agreeing that Riot can ban your account at any time for any reason they like.

Is this true? Or is it all just a bunch of bull****?
I wish to send a personal report because this guy was just the most incessantly annoying and toxic players I've ever seen.
They would ***** about how their AD fed first blood, then spend the rest of the game TYPING and zoning themselves, then complaining even more about how they lost the lane.
I wanted to rip my eyes out.

I have their username saved in a special place in my heart. I await the day that they come to the forums *****ing about how Riot illegally banned them or something.
Then I will present a replay of said game.

"Literally they cannot ban me".

In other news, did that sona have gp10 runes and masteries cause i didn't think it was possible to be so poor. I mean you gen even when you're dead so those 5 deaths shouldn't have nerfed her income at all.

If you don't accept the agreement after a patch you can't play as far as I know. So, yeah, he can get banned. And even if, hypothetically, he didn't accept the Summoner's Code, that actually means Riot could ban him without warning and for no particular reason.